The present invention relates to a magnetic recording and reproducing apparatus for recording or reproducing data on a magnetic tape and more particularly to the apparatus that is arranged to save an electric power consumed in detecting a tape end and reduce a load on a microprocessor provided in the apparatus.
No light is allowed to pass through a tape on which magnetic substance is coated or evaporated. Hence, the magnetic recording and reproducing apparatus according to the prior art has arranged to use a magnetic tape having a light-transmittable, transparent area (called a leader tape) on the end of the tape. That is, the apparatus provides a light emitting circuit and a light receiving circuit. In operation, the light emitted by light emitting circuit passes through the light-transmittable area and is sensed by the light receiving circuit for detecting the ends of the tape.
As this kind of apparatus, a VTR is described in xe2x80x9cIntroduction to Home VTRxe2x80x9d, edited by Corona Publishing Co., Ltd., 1981, pp. 123 to 133.
The foregoing prior art, however, needs to actuate the light emitting circuit for emitting light continuously or periodically (at predetermined time intervals of time according to the switching operation) at all times and actuate the light receiving circuit for receiving the light, for the purpose of detecting the end of the tape in the same manner. The prior art is, therefore, disadvantageous in that both the light emitting circuit and the light receiving circuit have to constantly consume an electric power.
Further, the apparatus of the prior art provides an analog-to-digital converter (called an AD converter) loaded on a microprocessor, through which an output signal sent from the light receiving circuit is converted into a digital signal. Based on the digital signal, the presence or absence of light is determined. To execute this operation, the conventional apparatus is required to periodically operate the AD converter and a program for analyzing a digital value. This has been a continuous or periodic burden on the microprocessor.
To overcome this shortcomings, it is an object of the present invention to provide a recording and reproducing apparatus that is arranged to reduce the power consumption and/or load on a microprocessor provided in the apparatus.
In carrying out the object, a magnetic recording and reproducing apparatus according to an aspect of the invention provides means for sensing a current taken-up position of a magnetic tape. If the current taken-up position sensing means determines that the tape taken-up position is close to the end of the tape, the light emitting circuit is operated continuously or at predetermined intervals. If the taken-up position sensing means determines that the tape taken-up position is distant or away from the end of the tape, the light emitting circuit is made inoperative for saving the power consumption of the circuit.
If the taken-up position sensing means determines that the current tape taken-up position is close to the end of the tape, the apparatus operates to supply electricity to the light receiving circuit. If the taken-up position sensing means determines that the tape taken-up position is distant from the end of the tape, the apparatus operates to stop the distribution of electric power (called power distribution) to the light receiving circuit for saving the power consumption in the circuit.
Further, in the case of sensing the tape end through a microprocessor by analyzing the output signal of the light receiving circuit to determine the presence or the absence of passed light on the analyzed result, if the taken-up position sensing means determines that the current tape taken-up position is close to the tape end, the microprocessor is enabled for analyzing the received-light signal. If the taken-up position sensing means determines that the current tape taken-up position is distant from the tape end, the analyzing operation of the received-light signal is stopped for reducing the load on the microprocessor.
As described above, the magnetic recording and reproducing apparatus of the present invention has the foregoing means. Hence, the apparatus enables to turn off the light emitting elements for sensing the tape end and stop the power distribution to the light receiving circuit on most of the entire tape length while the tape is running. This makes it possible to greatly save the power consumption. In the case of apparatuses which use a microprocessor to analyze the received-light signal and sense the tape end based on the analyzed result, it becomes possible to stop the analyzing program on most of the entire tape length while the tape is running, thereby greatly reducing the load on the microprocessor.